Among other uses, electromagnetic drives are used to drive hydraulic slide valves, particularly for the opening and closing of valves. In this regard, a differentiation is made between low-pressure systems in the range of 3-25 bar, medium-pressure systems in the range of 25-65 bar and high-pressure systems in the range of 65-200 bar. Hydraulic valves operating as low-pressure systems in the range of approximately 10 bar are known in the prior art. Actuating drives for valves in low-pressure systems are larger and heavier than actuating drives in high-pressure systems.
From cost perspectives as well as technical perspectives, there is increasing need for new high-pressure system drives having smaller valves. Compared to low-pressure systems, high-pressure systems have the advantage of the fluids employed exhibiting lower pressure, turbulence and acceleration losses. Moreover, smaller components can be used in high-pressure systems, by which an optimizing of costs can likewise be achieved along with being able to save space. However, actuating drives in high-pressure systems must be able to apply greater forces relative to their dimensioning.
Actuating drives for high-pressure applications which use e.g. coils with a permanent magnet and are able to implement a bidirectional motion; i.e. the electric coil moves the permanent magnet in one or the opposite direction, are already known in the prior art. However, such drives are of relatively large dimensions. Smaller drives in the prior art are in turn not capable of providing the force necessary in high-pressure systems for the lifting axis to have sufficient power reserves against potential contaminants infiltrating the pressure medium.
As is known, an electromagnet of an actuating drive comprises a coil which generates a magnetic field via current as well as a core and an armature. The wire of a coil is routinely circularly coiled. The core of an electromagnet consists of a soft magnetic material, in the simplest case soft iron. The core serves in the bolstering and/or amplifying of the magnetic field. The armature of the electromagnet is ferromagnetic and is energized by the magnetic field generated by the coil and amplified by the core. The magnetic field formed between the armature and core exerts a force which is dependent on the air gap and/or distance formed between the armature and core and essentially corresponds to a hyperbolic characteristic; i.e. the smaller the distance between the core and armature, the stronger the magnetic force. This force increases essentially asymptotically as the distance between the core and armature decreases.